Well apparatus



y 1966 J- w LUBBES 3,250,578

WELL APPARATUS Filed Jan. 27, 1964 Mack W. 045,619;

INVENTOR.

ATTORNEY Filed Jan. 27, 1964, Ser. No. 340,363 3 Claims. (Cl. 3084) Thisinvention pertains to drill collars and more particularly to stabilizerdrill collars, useful in the rotary system of earth drilling, e.g. indrilling oil and gas wells.

Heretofore it has been customary to employ conventional stabilizers inbetween drill collars to maintain the drill collars concentric with thehole already drilled, thereby to continue drilling in a straight line.Because the stabilizers are relatively short in length, e.-g. one or twofeet, compared to the twenty to thirty foot length of the usual drillcollar, there is still considerable opportunity for side play andeccentric positioning of the drill collars, and also for bending andwhip of the drill collars in between the stabilizers.

The difliculty with conventional stabilizers is aggrevated if theformation being drilled is unconsolidated or shifting, resulting incave-ins. The resultant enlargements in the hole being drilled must betraversed by the stabilizers as drilling proceeds and when a stabilizeris'in an enlarged portion of the holeit becomes ineffective.

According to the present invention the aforementioned difliculties areovercome by providing the drill collar with stabilizing meansdistributed along substantially the entire length of the drill collar.

Conventional stabilizers comprise tubular bodies with connecting meansat each end whereby the stabilizer body can be connected in the drillstring to transmit mechanical forces and convey fluid between theadjacent portions of the drill string. The outer periphery of the bodyis provided with radially extending means, such as ribs, to

United States Patent contact the wall of the holes being drilled,thereby to I prevent lateral movement of the tubular body and kee itconcentric with the hole. The spaces between the ribs provide fluidpassages in which annulus fluidcan pass by the stabilizer. Thelongitudinal extent of such ribs varies from two to four times thediameter of the well bore, or otherwise expressed, the length of theribs is of the same order of magnitude as the circumference of the wellbore.

-In contrast thereto, the wall contacting means of the present inventionis a whole order of magnitude longer, extending some ten times thecircumference of the hole being bored. This in itself presents problems.As is stated in US. Patent 2,829,864 on a Method and Apparatus forStraightening Well Bore Holes: Use of oversized drill collars andreamers often causes crowding of jamming of the drill string. (Col. 1,lines 33-34.) The crowding results in poor fluid flow in the annulus andthe loss of fluid flow is a cause of jamming.

According to the present invention, adequate annulus flow is assured bythe combined action of three structures:

('1) Only four wall contacting ribs, each having'only about 30 degreescircumferential extent, leaving an adequate passage about 60 degrees,between each adjacent pair of ribs, for fluid flow.

(2) The sides and bottoms of each fluid passage between the ribs are onecontinuous concave surface, e.g., comprising a segment of a cylinder,eliminating any sharp corners wherein mud might be caught and build up aflow restricting plug.

(3) At intervals along the length of the drill collar all the ribs areinterrupted leaving an annular fluid passage extending all around thedrill collar interconnecting the longitudinal passages between the ribs,whereby if there is any blockage in one of the longitudinal channels,the effect thereof is minimized, in that the blockage does not cut offfluid flow for the whole length of the drill collar.

A further feature of the invention is the circumferential displacementor offsetting of the ribs at each of the interruptions forming theannular fluid passages. Thus, despite the fact that only four ribs, eachof but 30 degrees circumferential extent, are employed, there isprovided wall contacting means over a major portion of the circumferenceof the drill collar. Nevertheless, due to the interruptions andoffsetting of the ribs, there is less likelihood of the drill collarbecoming jammed in the hole.

The ribs may be provided with hard facing, i.e. tungsten carbide, toprevent wear on the ribs as drilling proceeds, the diameter at the ribperipheries being almost full gage, e.g., 8%" for an 8%" hole. Usingadrill collar of this near approach to full gage constitutes what iscalled packed hole drilling.

To distinguish the subject drill collar from ordinary drill collars, thepresent drill collar may be referred to as a packed hole drill collar ora stabilizer drill collar. In an ordinary drill collar the outerdiameter is the same as that of the threaded box provided at one endthereof for connection to other parts of the drill string, whereas thestabilizer drill collar of the present invention has a diameter at theouter periphery of the ribs that is considerably larger than the box atone end of the collar, in fact the groove bottoms have about the sameradial extent from the collar axis as the outer periphery of the box.

For a detailed description of a preferred embodiment of the inventionreference will now be made to the accompanying drawing wherein:

FIGURE 1 is an elevation of a stabilizer drill collar embodying theinvention, same being shown connected to a drill bit;

FIGURE 2 .is a horizontal section taken at plane 22 of FIGURE 1; and

FIGURE 3 is a horizontal section taken at plane 3-3 of FIGURE 1.

Referring now especially to FIGURE 1 there is shown a stabilizer drillcollar including a tubular body 10 hav ing a fluid passageway 11therethrough (see also FIG URES 2 and 3). At the upper end of the bodythere is provided means for connecting the drill collar to another partof a drill string, said means being in the form of a threaded box 12.Means for connecting the drill collar to another part of the drillstring is also provided at the lower end'of the drill collar, this meansbeing in the form of a threaded pin 13. As shown, pin 13 is connected toa double box sub 14, which in turn is connected to a drill bit 15. Ifdesired, the lower end of the drill collar could be provided with a box,similar to box 12 formed at the upper end thereof, thereby eliminatingthe need for sub 14.

Between the upper and lower ends of the drill collar it is provided witha plurality of longitudinally spaced groups of longitudinally extending,circumferentially spaced ribs, there being four ribs in each group.Regardless of which group a rib is in, it is designated by referencenumber 20. As shown in FIGURE 1, the radial extent of the rib 20 issubstantially the same as that of the bit 15, in practice the ribs mighthave the same or slightly less, e.g., /2", /16", or /s less, radialextent that the bit according to the preference of the user, as dictatedby operating conditions. In any case the radial extent of the ribs willbe considerably greater than that of box 12 and the land 21 adjacent pin13.

Between each adjacent pair of ribs there is formed a longitudinal fluidpassage 22. As best shown in FIG- UR'ES 2 and 3, these passages areconcave channels, whose surfaces are segments of cylinders. T he bottomsland 21 and the adjacent group of ribs 22. At the upper end of the drillcollar there is an annular necked down portion 27 with a shoulder 28therebove providing space and means for engagement of the upper end ofthe drill collar by elevators. It is to be noted that not only is thecontinuity of the longitudinal extent of the ribs 22 interrupted by theannular channels 25,- whereby the ribs are disposed in longitudinallyspaced apart groups, but in addition the ribs in each group arestaggered relative to those in each adjacent group, the j ribs in onegroup being aligned with the longitudinal fluid channels in the adjacentgroups.

Areas at the outer periphery of ribs may be provided with hard facing asshown at 30. Any suitable form of hard facing such as tungsten carbide,may be used. The ribs are of about thirty degrees circumferen tialextent'compared with about sixty degrees circumferential extent of thelongitudinal channels, there being four ribs and four channels pergroup.

While a preferred embodiment of the invention has been shown anddescribed, modifications thereof can be made by one skilled in the artwithout departing from the invention.

That being claimed is:

1. A stabilizer drill collar comprising a tubular body having threadedconnection means at each endfor connection to a drill string, aplurality of longitudinally spaced groups of circumferentially spacedlongitudinally extending ribs disposed along the length of the body,

being aligned with the longitudinal passages between the ribs in theadjacent groups of ribs, said groups of ribs and annular fluid passagesextending substantially the full length of said drill collar fromadjacent the threaded connection means atone end of the drill collar toadjacent the threaded connection means at the other end of the drillcollar, their being four ribs in each group, the circumferential extentof each longitudinal fluid pass-age being of the order of twice thecircumferential extent of each r-ib.

2. The combination according to claim 1 wherein said annular andlongitudinal fluid passages are concave, the bottom of said passagesbeing of less radial extent than that of the-outer periphery of saidthreaded connection means.

3. The combination according to claim 1 wherein said ribs are ofsubstantially full gage with respect to the hole to be bored, comparedto the lesser diameter of the threaded connection means, and areprovided with bar facing at their outer peripheries.

References Cited by the Examiner UNITED STATES PATENTS 349,192 9/ 1886Woodhouse 17523 1,031,643 7/ 1912 Hahn 246-210 1,374,946 4/ 1921Nebergal-l 308-4 2,188,119 1/ 1940 Prentice 166233 2,466,239 4/ 1949Holcombe 166-176 DAVID J. WILLIAMOWSKY, Primary Examiner.

L. L. IOH-NSON, Assistant Examiner.

1. A STABILIZER DRILL COLLAR COMPRISING A TUBULAR BODY HAVING THREADEDCONNECTION MEANS AT EACH END FOR CONNECTION TO A DRILL STRING, APLURALITY OF LONGITUDINALLY SPACED GROUPS OF CIRCUMFERENTIALLY SPACEDLONGITUDINALLY EXTENDNG RIBS DISPOSED BEING THE LENGTH OF THE BODY, SAIDRIBS EXTENDING RADIALLY BEYOND THE OUTER PERIPHERY OF EACH OF SAIDTHREADED CONNECTION MEANS, AN ANNULAR FLUID PASSAGE AROUND THE BODYBETWEEN EACH PAIR OF ADJACENT GROUPS OF RIBS, A LONGITUDINAL FLUIDPASSAGE FORMED BETWEEN EACH PAIR OF ADJACENT RIBS, THE RIBS IN EACHGOURP BEING ALIGNED WITH THE LONGITUDINAL PASSAGES BETWEEN THE RIBS INTHE ADJACENT GROUPS OF RIBS, SAID GROUPS OF RIBS AND ANNULAR FLUIDPASSAGES EXTENDING SUBSTANTIALLY THE FULL LENGTH OF SAID DRILL COLLARFROM ADJACENT THE THREADED CONNECTION MEANS AT ONE END OF THE DRILLCOLLAR TO ADJACENT THE THREADED CONNECTION MEANS AT THE OTHER END OF THEDRILL COLLAR, THEIR BEING FOUR RIBS IN EACH GROUP, THE CIRCUMFERENTIALEXTENT OF EACH LONGITUDINAL FLUID PASSAGE BEING OF THE ORDER OF TWICETHE CIRCUMFERENTIAL EXTENT OF EACH RIB.